Sunday, March 23, 2008

Check Ride In the Archer... Again

It has been almost a year since I flew the Archer. It is the policy of the rental company that I take another check ride. That is fine with me. I would have taken an instructor up anyway. I would rather pay the extra money than end up dead.

I thought that today would be a nice day with light winds. No such luck in Nebraska, where the wind always blows. Today is especially nasty, because the wind direction is just off to the left of the runway direction giving me an annoying cross-wind to deal with. On top of this we have wind gusts. That sucks.

Wind gusts suck, because they are not steady, and can change and any second. With a quartering cross wind you could be dead on the center of the runway and suddenly you are landing on the taxi way because you had correction in for a 20 knot wind that just went to 10 knots. Even worse you had correction in for 10 knots and it changed in to 20 knots when you are most vulnerable, right before touchdown in the flair.

Most of the time, you don't just fly the airplane in to the ground to land it. You have to have a little bit of finesse and timing to land. You don't want to land with too much speed, you could end up floating, or nose over, or some other nastiness that will kill you.

It all comes down to this: the airplane will fly at what ever speed the power and angle of attack will allow it to. To slow down you have to reduce power, or add angle of attack. To speed up you have to add power, or reduce your angle of attack. Your angle of attack is controlled by your elevators, which you control by pushing in your yoke/stick to lower the nose, pulling back to raise the nose.

So, as you descend on to the runway on your short final, you are generally in a low power, slow speed, nose down configuration. The idea is to use power to control your rate of decent and pitch to control your airspeed. Remember the airplane will fly at what ever speed the power setting and the angle of attack is set for. There is a "magic" speed that you can achieve where at the right nose configuration and the right power setting you do not gain or loose altitude.

The ideal is to be hanging out just above the airplane's stall speed (the speed at which the wings can no longer support lift) and keep it there with pitch. Nose down you gain speed, nose up you loose speed. The addition of flaps to this configuration increases the amount of lift the wing has. So by adding power you give the airplane more lift.

Wind, essentially, adds, or removes, power to the configuration by pushing the aircraft forward or backward depending on the direction of the wind. During take off or landing you always want to fly in to the wind. This additional air flow reduces your ground speed, how fast you are moving over the earth's surface, but increases your airspeed, how fast the air is moving across your wings. This greatly affects how you land. A high wind that suddenly is not there is just like pulling your power completely off, your airspeed plummets and so do you. Not very fun.

To compensate for that you need to carry more speed in to the gusty landing than you normally would. The rule of thumb is to carry half the gust spread. So if we have a 10 knot steady wind, gusting to 20 knots, the gust spread is 10 knots. Half of that is 5 knots. So if I normally shoot for a speed of 65 knots when landing I would need to shoot for 70 knots to compensate for the gusty wind.

It should be fun.

Nice shot of an Archer II waiting for a Tomahawk to land at Scappoose Industrial Airpark - KSPB Oregon